Transcript Lecture 12
Ecology: Animal Interactions Trophic Pyramids and Trophic Webs Review of Energy Principles • Photosynthesis – converts light energy into chemical energy (glucose). • Respiration – converts chemical energy (glucose) to chemical energy (ATP). • Laws of Thermodynamics – 1st Law – conservation of energy, all energy must be accounted for – 2nd Law – order to disorder heat What is Ecology? study of the interaction between abiotic and biotic components of…… How do non-photosynthetic organisms capture energy? • They eat! • What happens to some of the energy that they acquire? What is it turned into? • What do they eat? • Where does the energy in what they eat come from? The Sun Light Energy Fates • Reflectance • Absorption by nonphotosynthetic systems • Radiated back to space • Absorption by photosynthesis Let’s follow the sun’s energy • Let’s just follow it through Photosynthesis – Step 1: light energy absorbed by photosynthesis – Step 2: photosynthetic process (light dependent reactions) – Step 3: energy is now in form of glucose and can be stored in other carbohydrate forms (starch, cellulose, etc.) • If glucose is eaten by an animal it can remain as glucose or stored as either glycogen or chitin Light energy Carbon dioxide Water Photosynthesis Glucose Oxygen gas Terrestrial Food Chain (Step 4) Aquatic Food Chain (Step 4) Direction of Energy Flow Energy Pyramid • Since the heat is no longer useful, at each step, the amount of useful energy from our original burst of sunlight is reduced. Energy • Energy passes through biological systems – Energy enters the system via photosynthesis – Energy passes through the biological system through trophic levels via metabolism (cellular respiration) – Energy leaves the biological system in the form of heat. Energy does not flow linearly - Food Webs Interactions Between Organisms Interaction type • Interspecific interactions are 1. Herbivory interactions between species. Effect on Target Beneficial Harmful Beneficial Harmful Harmful Harmful Parasitism Beneficial Harmful Commensalism Beneficial Neutral Mutualism Beneficial Beneficial 2. Predation • Intraspecific interactions are interactions within the same species. Effect on Actor 3. Competition 4. Symbiosis 1. Herbivory • Herbivory - the interaction is beneficial to the actor but harmful on the target • Herbivore • Omnivore 2. Predation • Predation- the interaction is beneficial to the actor but harmful on the target • Carnivore • Omnivore Predation effect on species diversity within a community ecosystem With Pisaster (control) Without Pisaster Competition • The effect on the actor is harmful and the effect on the target is harmful High tide Chthamalus Balanus Ocean Low tide Chthamalus can live lower on the shore but doesn’t because it is competitively displaced by Balanus. Higher mortality of juvenilles as well. Symbiotic Interactions • Parasitism- effect on the actor is beneficial and harmful on the target. Commensalism • The effect on the actor is beneficial and the effect on the target is neutral. The Cattle Egret (Bubulcus ibis) forages in pastures and fields among livestock such as cattle and horses, feeding on the insects stirred up by the movement of the grazing animals. The egrets benefit from the arrangement, but the livestock, generally, do not. Mutualism • The effect on the actor is beneficial and the effect on the target is beneficial Bird benefits by getting food while buffalo benefits from removal of potential parasites. You should be able to: • Follow energy from the sun through a food chain or food web, and identify the conversions that happen. • Use a food web or food chain to identify the trophic relationships of represented organisms. • Identify the immediate source of energy for an organism and the original source of energy for all organisms. • Explain the role of detritivores in a food chain or food web. • Explain why the energy pyramid is shaped the way it is. • Explain/identify how different types of interactions affect both of the organisms involved.